Yoshihiro Mitsutsuka

Selective determination of haloperidol in human serum : surface ionization mass spectrometry and gas chromatography with surface ionization detection

Surface ionization organic mass spectrometry (SIOMS) has been performed on the clinically important drug haloperidol using quadrupole mass spectrometry in which the thermal ion source has a rhenium oxide emitter. The surface ionization (SI) mass spectrum is presented, interpreted in a purely empirical way by means of evidence from previous investigations, and then compared to results from conventional electron impact (EI) ionization. An approach to detection of this drug in serum by gas chromatography (GC) with a surface ionization detector (SID) and GC-SIOMS is described. This approach demonstrates that (a) haloperidol is efficiently surface-ionized, giving a unique SI mass spectrum, (b) experimental results rationalize the combined sensitivity and selectivity of the GC-SID for the examined drug, (c) the detection limit for haloperidol in serum is 1.1 ng/ml (S/N = 3) by GC-SID (the coefficients of variation of the assay are generally low, i.e., below 8.5%) and (d) the GC-SIOMS coupling can be used for sensitive and selective detection of haloperidol in serum.

Photoassisted defluorination of fluorinated substrates and pharmaceuticals by a wide bandgap metal oxide in aqueous media

Persistent fluorinated substances, such as the fluorine-bearing pharmaceutical drugs Fluoxetine (FLX; Prozac) and Fluvoxamine maleate (FOM) together with several other substrates (fluorobenzoic acid and fluoroaliphatic model compounds), were photochemically defluorinated and degraded under UVC illumination in relatively good yields in the presence of a wide band gap metal oxide (β-Ga2O3) in heterogeneous aqueous media. The formation of fluoride ions increased with increasing illumination time under an inert nitrogen atmosphere, the transformation of the aromatic moiety was slower under these conditions, but nonetheless it did occur. The optimal amount of β-Ga2O3 loading for defluorination was 50 mg in aqueous media (0.10 mM, 100 mL); the optimal pH to defluorinate FLX was pH 6. Platinization (1 wt%) of the gallium oxide particles enhanced defluorination under an inert nitrogen atmosphere, but was decreased under an oxygen atmosphere; however, in the latter case the degradation of the substrates was facilitated as witnessed by loss of the aromatic moiety. The Ames test on the intermediate products from the photodegradation of FLX and 4-(trifluoromethyl)benzoic acid after long illumination times revealed that none were mutagenic.

Surface ionization mass spectrometry of biomolecules: amino acids, purine bases, alkaloids

Abstract Surface ionization organic mass spectrometry has been applied to a variety of biologically important molecules by using a quadrupole mass spectrometer in which the thermal ion source has a rhenium oxide emitter. Selected examples are presented to illustrate the potential and limitations of the method in the fields of biomolecules, amino acids, steroids, carbohydrates, purine bases and alkaloids. The techniques are apparently useful for amino acids, purine bases and alkaloids, but not for steroids and carbohydrates. The mass spectra appear unfamiliar when compared with conventional electron impact techniques. Interpretation is attempted in a purely empirical way. Experimental evidence is used to rationalize thermal dissociation followed by surface ionization of thermally dissociated species on the rhenium oxide surface.

Surface ionization mass spectrometry of organic compounds Part 4. Oxygen-containing organic compounds

Abstract Surface ionization organic mass spectrometry (SIOMS) was performed for 42 oxygen-containing organic compounds not previously investigated, using a quadrupole mass spectrometer in which the thermionic ion source has a rhenium oxide emitter. The results are interpreted in terms of the modes of ion formation: molecular surface ionization, dissociative surface ionization and associative surface ionization. SIOMS is particularly well suited to molecular weight and structural determination of aliphatic aldehydes. However, in general, most of the oxygen-containing compounds have lower sensitivities than nitrogen-containing compounds, but still provide some applications for SIOMS.

Photochemical and Ga2O3-photoassisted decomposition of the insecticide Fipronil in aqueous media upon UVC radiation

Fipronil is a phenylpyrazole-based insecticide and one of the relatively new widely used generations of insecticides whose biochemical action differs from the more traditional insecticides such as the organo-phosphates and -carbamates. Although several studies have been reported to determine the fate of Fipronil under environmental field conditions, including irradiation with UVB/UVA natural or simulated sunlight (wavelength >290–300 nm), which resulted in the formation of products that retained the basic phenylpyrazole structure, the present article examines the photodegradation of Fipronil upon irradiation of aqueous solutions under both reducing (nitrogen) and oxidative (air oxygen) atmospheric conditions at 254 nm (UVC; low-pressure Hg lamp), and for comparison purposes in the presence of the wide band-gap (4.8–5.0 eV) gallium sesquioxide (β-Ga2O3) semiconductor (and for comparison also TiO2). The fate of the insecticide under such conditions was ascertained by absorption spectroscopy in the UVC spectral region, by HPLC techniques for the desulfonation, defluorination, dechlorination and formation of both nitrate and ammonium ions, in addition to ESI-TOF-MS mass spectral methods to identify some of the possible intermediates that may have formed following the breakup of the phenyl and pyrazole rings. Mass spectra indicated that within 30 min filoprin was converted to Fipronil-desulfinyl (loss of SO fragment; photoproduct (III)) and in less than 1 hour of irradiation a significant quantity of the insecticides photoproduct (III) had also decomposed as no significant mass peaks were seen above m/z = 319. The largest yields of SO42− (79%), F− (44%), Cl− (33%), NO3− (34%) and NH4+ (15%) were obtained under air-equilibrated conditions in the presence of the metal oxide β-Ga2O3 (Ga2O3/O2), followed by air O2, Ga2O3/N2 and under N2 atmospheric conditions. Frontier electron densities and partial charges on all the atoms of Fipronil were calculated (hf/6-31g* configuration; Gaussian 09 software) to infer a possible, albeit not detailed, pathway(s) for the direct photolysis and when the metal oxides were involved in the photodegradation. In addition, Ames tests were carried out on the intermediate products of the photodegradation of Fipronil after 3 h and 24 h of UVC illumination; none of the intermediates displayed mutagenic activity.

Bond Cleavage of Nitrogen-Bearing Organics with "Molecular Scissors" of Titania for Aquatic Remediation

The first patent and paper in the world on the photocatalytic decomposition of organic compounds by TiO2 semiconductor were issued in 1959 by Kato and Masio (1, 2), which have an academic priority in this field. Since then, the photocatalytic remediation by TiO2 semiconductor has been widely studied and employed both in the abatement of widespread organic pollutants and in obtaining information on naturally occurring transformations. Nevertheless, several mechanistic aspects have not been revealed despite their extensive applications. One of these points is represented by the fate of bound nitrogens, for which the mineralization into inorganic ions of NH4and NO3 has been observed, but the detailed mechanism of their formation has not been elucidated until now. The comprehension of all the possible pathways involved in the natural evolution of nitrogen-containing substrates is extremely important not only because nitrogen constitutes a key element of the nutrient cycling but also because a large number of living organs contain one or more nitrogen atoms. The final fate of organic nitrogen(s) under photocatalytic processes is essentially dependent on the initial oxidation state of nitrogen in the organics, on the presence/absence of oxygen or on the structure of the organic compound (3, 4). This presentation deals with the fate of nitrogen initially present as amido group, under photocatalytic conditions to give the different ratio of the NH4+ and the NO3ions evolution. The basic principles of photocatalysis will be only briefly mentioned at present. The primary photophysicochemical event, following the near-UV light absorption by TiO2 (λ< 380 nm) is the generation of electron/hole pairs in the bulk Materials Science Forum Online: 2005-06-15 ISSN: 1662-9752, Vols. 486-487, pp 45-48 doi:10.4028/www.scientific.net/MSF.486-487.45

Organized assembly from biosurfactants

The formation of higher order aggregates in aqueous media from naturally occurring surfactants (biosurfactants) and its mechanism have been studied. A liposome (vesicle), as a kind of artificial cell, is prepared according to a newly developed microencapsulation technique from phospholipids by mimicking the molecular structure of biomembranes. Secondly, the surface active properties of alkaline salts of spiculisporic acid depend on the kinds of alkali as its gegen ions; these have been studied for the purpose of a detailed understanding of vesicle formation of the alkylamine salts of spiculisporic acid in the binary system consisting of spiculisporates and water. Thirdly, the solution behavior of the ternary system of spiculisporates-oil-water is examined. Divalent cationic salts of spiculisporic acid formed oil-in-water (O/W) emulsion gels due to ionic-bonding network formation of spiculisporates around emulsified oil droplets and these are important for their gelling properties. These gelling systems may have potential to be O/W emulsion-type paints and safe fuels.